How To Find and Overcome Shell Command Line Length Limitations

The maximum length of a shell command line is determined by the ARG_MAX limit, which is a system-wide limit on the maximum length of the command line, as well as the environment variables and other data that are passed to a command. The ARG_MAX limit is usually defined in the limits.h header file, which is included in the C standard library.

To find the ARG_MAX limit on your system, you can use the getconf command with the ARG_MAX option. For example, the following command will show the ARG_MAX limit on a Linux system:

getconf ARG_MAX

The getconf command will output the ARG_MAX limit in bytes, so you can calculate the maximum length of the command line in characters by dividing the ARG_MAX value by the size of a character (usually 1 byte).

If you need to overcome the ARG_MAX limit on the length of the shell command line, you can use one of the following methods:

• Use a shell builtin or external command that can accept the input as a file or standard input. For example, the grep command can accept the input as a file or standard input, so you can use it to search for patterns in a large file or stream of data without exceeding the ARG_MAX limit on the command line.
• Use a shell script to break the command into multiple smaller commands that each fit within the ARG_MAX limit. For example, you can use a for loop in a shell script to process each line of a large file or stream of data separately.